Current systems use raster-based display refresh techniques to update their displays. Using this technique, a host computing device transfers the entire displayed contents to the display device at a fixed rate, which is often called the “refresh rate” and is typically 60-85 Hz in prior systems. Each transfer typically moves a frame, also called a screen image, from the host to the display device by tracing the screen image from left-to-right and top-to-bottom on the display screen. This refresh is wasteful unless substantial portions of the screen image change at approximately the refresh rate.
For example, consider a user reading a news story from a web page. The content of the displayed page changes only as the user scrolls through the story; yet, current systems built on raster-refresh techniques expend energy and effort to repeatedly copy the same data, i.e., the screen contents, from the host to the display. This repeated copying inefficiently uses power and bandwidth between the host and the display.